diff --git a/.claude/CLAUDE.md b/.claude/CLAUDE.md
index 98b1774..e04c550 100644
--- a/.claude/CLAUDE.md
+++ b/.claude/CLAUDE.md
@@ -120,12 +120,38 @@ Every skill, agent and hook is held to these; a change that breaks one says why.
   header row, so rename or renumber any of them only with those citations.
 - The Python environment is uv's (`pyproject.toml`, `.python-version`; the devcontainer and CI run
   `uv sync`). The dev tools' pins live in `pyproject.toml` only; `uv.lock` is not committed.
-- Before a pull request: `uv run python -m unittest discover -s tests`, the five
-  `tests/*.sh`, and `uv run python scripts/check_static.py`, so the tests use the project's
-  environment outside the devcontainer too; CI also runs codespell, `claude plugin validate .`, and the unit tests and `check_static.py`
-  on Python 3.9, the README's floor.
+- Before a pull request: `bash tests/checks.sh`, scoped as the next bullet says.
   A change to what a skill, agent or hook does fills the description's `Origin:`, `Sandbox:` and
   `Canary:` lines, as the README's "Changing the tooling" says; a `skill-feedback` issue is where
   a complaint about a skill starts.
+- Checking scales with the depth of the change. CI runs every check on every pull request, so
+  locally `bash tests/checks.sh` runs the tests that name a changed file or a script loading it,
+  and the static checks, as its header sets out; `--all` reproduces CI when it is red. Run the
+  checks serially: in parallel they produce spurious errors.
+
+  | Change | Before review | Sandbox | Adversarial review |
+  | --- | --- | --- | --- |
+  | Docs, ROADMAP, CI, devcontainer, the checks runner | `checks.sh` (static only) | None | None; the PR reviewer |
+  | A script, hook or test that changes no skill's output | `checks.sh` | None | One round |
+  | A skill's or agent's behavior or wording | `checks.sh` | `compare` on the scenarios that state the change, one Haiku batch; `--check --repeat 2` before the merge | Rounds until clean |
+  | A gate, or anything that posts or writes outside the repository | `checks.sh --all` | As above, plus the gate's scenarios; the week's canary | Rounds until clean |
+
+  The README's "Changing the tooling" owns the `Origin:`, `Sandbox:` and `Canary:` lines a pull
+  request carries; this table only says what to run.
+
+  While iterating, `bash tests/checks.sh <name>...` runs one module; the default runs before
+  review and after its fixes, not after every edit.
+- Usage per turn grows with the context the turn carries, so long sessions and agents are the
+  cost, not the checks or the sandbox:
+  - One agent per phase, started fresh: implement, gather sandbox evidence, fix review findings.
+    Each gets the plan, the review file or the scenario list and reports through files. A new
+    ticket starts a new main session.
+  - An agent doing mechanical work, such as running a sandbox batch and tabulating its summaries
+    or rerunning one failing test against a known fix, is spawned with `model: sonnet`. Planning,
+    implementing and reviewing keep the session's model.
+  - A command that takes minutes runs in the background and is waited on through its completion
+    notice, never a `sleep`, `pgrep` or repeated `tail` loop.
+  - Reading is batched: several `sed -n` ranges or greps in one call, and a wide search goes to
+    an Explore agent.
 - `ROADMAP.md` holds deferred and planned work. An item leaves it when it lands, and a change that
   defers or lands one updates it in the same change.
diff --git a/README.md b/README.md
index 29122e8..f6adbae 100644
--- a/README.md
+++ b/README.md
@@ -910,6 +910,14 @@ CI (`.github/workflows/checks.yml`) runs, on every pull request:
 - codespell, with `en-GB_to_en-US`, for American spelling.
 - `claude plugin validate .`, on the plugin and marketplace manifests.
 
+Locally, `bash tests/checks.sh` runs the tests of what the branch changed against
+`origin/main`, with `check_static.py` and codespell, one step after another, printing a line per
+step and the output only of a step that fails; its header says how a changed file maps to tests.
+`bash tests/checks.sh next_phase where` runs only `tests/test_next_phase.py` and
+`tests/test_where.sh`, and `--all` runs every step CI runs except its gitleaks scan of the
+history, with the installed `claude` in place of CI's pinned one. How much checking each kind of
+change gets is in `.claude/CLAUDE.md`.
+
 To try a skill change before its pull request, run it in [`sandbox/`](sandbox/README.md): the
 skill's scenario on a worktree of your branch beside the current plugin, repeated, then
 compared, and `--check --repeat 2` on it before the merge. Nothing there runs in CI.
diff --git a/tests/checks.sh b/tests/checks.sh
new file mode 100755
index 0000000..d720263
--- /dev/null
+++ b/tests/checks.sh
@@ -0,0 +1,134 @@
+#!/usr/bin/env bash
+# Runs the pull request checks one after another and prints one line per step; a failed step
+# also prints the last 40 lines of its output, and the full logs stay in the directory the last
+# line names. Serial on purpose: run together, test_profile, test_window_merges and
+# test_surface_diff fail on each other's temporary state.
+#
+#   bash tests/checks.sh            the tests of what the branch changes against origin/main,
+#                                   committed or not, then check_static.py and codespell:
+#                                   - a changed tests/test_* file;
+#                                   - for a script, hook or sandbox .py or .sh, every test file
+#                                     naming it, and every test file naming a script, hook or
+#                                     sandbox file that names it;
+#                                   - for any other file under scripts/, hooks/, sandbox/ or
+#                                     standards/templates/, every test file naming it, or the
+#                                     whole suite when none does;
+#                                   - the whole suite for tests/fixtures/, pyproject.toml or
+#                                     .python-version.
+#                                   Skills, agents and docs get the static checks only.
+#   bash tests/checks.sh NAME...    only tests/test_NAME.py or tests/test_NAME.sh for each NAME,
+#                                   such as `next_phase where`
+#   bash tests/checks.sh --all      CI's steps but its gitleaks scan: the mcp-atlassian cache, the
+#                                   unit tests, every tests/test_*.sh, check_static.py, both
+#                                   again on Python 3.9, codespell and `claude plugin validate .`,
+#                                   the last with the installed claude, not CI's pinned version
+#
+# Exits 0 when every step passed, 1 when one failed, and 2 for a NAME with no test file, a
+# missing tool, or no origin/main to compare with.
+cd "$(dirname "$0")/.." || exit 2
+# The tests make hundreds of throwaway commits. Without the person's git configuration they run
+# as on CI, which has none, and unsigned: a signing key there makes each commit about twice as slow.
+export GIT_CONFIG_GLOBAL=/dev/null GIT_CONFIG_NOSYSTEM=1
+logs=$(mktemp -d "${TMPDIR:-/tmp}/checks.XXXXXX") || exit 2
+home=""
+failed=0 n=0
+trap '[ "$failed" = 1 ] || rm -rf "$logs"; [ -z "$home" ] || rm -rf "$home"' EXIT
+
+step() {
+  local name=$1; shift
+  n=$((n + 1))
+  local log="$logs/$n-${name//[^A-Za-z0-9_.-]/_}.log" start=$SECONDS
+  if "$@" >"$log" 2>&1; then
+    printf 'ok    %-28s %3ss\n' "$name" $((SECONDS - start))
+  else
+    printf 'FAIL  %-28s %3ss\n' "$name" $((SECONDS - start))
+    tail -n 40 "$log" | sed 's/^/      /'
+    failed=1
+  fi
+}
+
+need() { command -v "$1" >/dev/null || { echo "checks.sh: $1 is not on PATH" >&2; exit 2; }; }
+
+run_test() {
+  case $1 in
+    *.py) step "$(basename "$1")" uv run python -m unittest discover -s tests -p "$(basename "$1")" ;;
+    *.sh) step "$(basename "$1")" bash "$1" ;;
+  esac
+}
+
+naming() { grep -l -F "$1" tests/test_*.py tests/test_*.sh 2>/dev/null; }
+
+static() {
+  step "check_static" uv run python scripts/check_static.py
+  step "codespell" uv run codespell --builtin clear,rare,en-GB_to_en-US --skip "./.git,./tests/fixtures" .
+}
+
+whole_suite() {
+  step "unit tests" uv run python -m unittest discover -s tests
+  for t in tests/test_*.sh; do
+    run_test "$t"
+  done
+}
+
+need uv
+if [ "$1" = --all ]; then
+  need uvx
+  need claude
+  step "mcp-atlassian cache" uvx --from mcp-atlassian@0.23.1 python -c pass
+  whole_suite
+  static
+  step "unit tests, python 3.9" uv run --isolated --python 3.9 python -m unittest discover -s tests
+  step "check_static, python 3.9" uv run --isolated --python 3.9 python scripts/check_static.py
+  home=$(mktemp -d) || exit 2
+  step "plugin validate" env HOME="$home" claude plugin validate .
+elif [ $# -gt 0 ]; then
+  tests=()
+  for name in "$@"; do
+    if [ -f "tests/test_$name.py" ]; then
+      tests+=("tests/test_$name.py")
+    elif [ -f "tests/test_$name.sh" ]; then
+      tests+=("tests/test_$name.sh")
+    else
+      echo "checks.sh: no tests/test_$name.py or tests/test_$name.sh" >&2
+      exit 2
+    fi
+  done
+  for t in "${tests[@]}"; do
+    run_test "$t"
+  done
+else
+  base=$(git merge-base origin/main HEAD 2>/dev/null) \
+    || { echo "checks.sh: no origin/main to compare with; name the tests or pass --all" >&2; exit 2; }
+  selected=$logs/selected
+  whole=0
+  : >"$selected"
+  while IFS= read -r f; do
+    [ -n "$f" ] || continue
+    name=$(basename "$f")
+    case $f in
+      tests/fixtures/* | pyproject.toml | .python-version) whole=1 ;;
+      tests/test_*.py | tests/test_*.sh) [ -f "$f" ] && echo "$f" >>"$selected" ;;
+      scripts/*.py | scripts/*.sh | hooks/*.sh | sandbox/*.py)
+        naming "$name" >>"$selected"
+        for loader in $(grep -l -F "$name" scripts/*.py scripts/*.sh hooks/*.sh sandbox/*.py 2>/dev/null); do
+          [ "$loader" = "$f" ] || naming "$(basename "$loader")" >>"$selected"
+        done ;;
+      scripts/* | hooks/* | sandbox/* | standards/templates/*)
+        naming "$name" >>"$selected" || whole=1 ;;
+    esac
+  done < <({ git diff --name-only --no-renames "$base"; git ls-files --others --exclude-standard; } | sort -u)
+  if [ "$whole" = 1 ]; then
+    whole_suite
+  else
+    while IFS= read -r t; do
+      run_test "$t"
+    done < <(sort -u "$selected")
+  fi
+  static
+fi
+
+if [ "$failed" = 1 ]; then
+  echo "full logs: $logs"
+  exit 1
+fi
+echo "all $n passed"